The invention relates to hand-operated shears with a ratchet mechanism.
Shears with ratchet mechanisms have the advantage that higher resistance forces of the material to be cut can be overcome with moderate hand force of the user than with shears with the same hand lever length without a ratchet mechanism. A design is especially customary in which in a first articulation a second hand lever and in a second articulation a second shears lever are connected to a first pivot lever that contains a first shears shaft and a first hand lever. The second shears lever contains a second shears cheek and a lever extension. The lever extension is connected via a ratchet lever to the second hand lever, whereby a first end of the ratchet lever is supported in a third articulation and the second end of the ratchet lever is supported on a ratchet structure with several ratchet steps. In a first ratchet position, in which the ratchet lever engages after the maximal opening position of the hand levers during the closing of the hand levers, the shears cheeks (e.g. blades) cannot be completely closed. The hand levers must be opened a little bit wider again after reaching the end position of a first closing operation of the hand levers, whereby the ratchet lever jumps under spring action to one of the next ratchet steps, in which in the end position of the hand lever closing operation a more extensive or complete closing of the shears cheeks is possible. Shears with such a ratchet mechanism are known, e.g. from DE 298 16 971 U1.
The multiple closing operations of the hand levers with partial opening to be carried out in between them are also necessary if the resistance of the material to be cut could also be overcome in a single closing operation of the hand levers, in the following as a direct cut, by the hand force that can be applied by the user on the hand levers. In such a case the multi-step cutting operation via the ratchet mechanism is unnecessarily expensive.
The GARDENA Comfort Ratchet Shears Smart Cut has a pivotable support lever on the second handgrip, with which support lever the end of the lever extension of the second shears lever, which end faces away from the second shears axis, can be supported against the second hand lever in a ratchet mechanism of the described type without the ratchet lever with the ratchet structure becoming effective in a force-transferring manner so that a direct cut can be carried out with an expenditure of force as in traditional garden shears. For stronger material to be cut the ratchet mechanism can be engaged by pivoting the support lever away and a cut can be made in several motions.
U.S. Pat. No. 6,470,575 B2 suggests, in order to avoid the multiple actuation of ratchet shears, the construction of a control cam on the lever extension facing the second hand lever, which cam is guided on two rollers arranged on the second hand lever during the closing operation carried out as a direct cut. However, this is only an attempt to optimize the expenditure of force via the course of a cutting operation during a direct cut. One according to the same principle but with a roller on the lever extension and with a control cam on the second hand lever is described in the MD 3065 F1. A distinct reduction of the required force by a multiple closing operation of a ratchet mechanism with a greater accumulative hand lever travel is not possible with these shears with control cam.